This invention is directed toward the art of safety caps for pressurized vessels and, more particularly, to an improved safety cap assembly for use on pressurized vessel equipment that is often used to clean the inside of plants having heavy residue.
Pressurized vessels are often provided with a closure cap or valve which, when removed, allows the tank to be filled with a liquid substance but which, when secured in place, allows the liquid within the tank to be pressurized. However, the removal of the closure cap subsequent to the pressurizing of the vessel may involve a sudden release of pressure as the cap is unscrewed. This sudden release of pressure creates a highly dangerous situation as it often results in the expulsion of some of the liquid from within the tank. Since the liquids used to clean plants having heavy residue are highly corrosive and, consequently, very harmful to the skin and eyes, it is quite apparent that should any of the liquid from within the tank be expelled by the sudden release of pressure, the person unscrewing the cap or opening the valve is subjected to serious bodily injury. In fact, there are instances in which persons unscrewing such closure caps or releasing a valve have lost their sight as a result of the cleaning liquid being expelled into their eyes by the sudden release of pressure.
Further, the sudden release of pressure upon removing the closure cap subsequent to the pressurization of the vessel is also highly dangerous in that it may result in the cap of the vessel being blown off. In effect, the cap may become a dangerous projectile or missile. The person unscrewing the closure cap is consequently subjected to the threat of serious bodily injury should the cap blow off the vessel as he unscrews it. In fact, there are instances in which persons unscrewing such closure caps have been injured. Such injuries range from minor cuts and bruises to serious injuries, such as the loss of an eye, the loss of a finger, broken limbs, our serious head injuries.
While pressurized vessels are often equipped with various devices for releasing vessel pressure to the atmosphere before the closure cap is removed, most vessels are not used in an extremely severe environment, such as that found in a food processing plant or with highly corrosive cleaning liquids. While there may be occasional problems with the operation of such pressure release devices in a normal environment, the operation of a food processing plant generates a considerable amount of dust, dirt and food residue, such as food protein and animal fat. In such dirty environments, past pressure release devices have often failed because the residue has impeded their functioning.
In fact, some of the failures of past pressure release devices have resulted from the dirt, dust and food residue generated during the cleaning process as well as corrosion by the cleaning liquid. Typically, the problem occurs because the spray of cleaning fluid generated by the pressurized vessel loosens and mixes with the dust, dirt and food residue of the food processing plant. This dust, dirt and food residue generated during the cleaning process then falls or splashes onto the cleaning equipment and becomes lodged on and in the pressure relief assembly of the cleaning equipment with the consequent result that bleed holes or safety valves included in the pressure relief assembly become inoperative.
Prior safety caps have used bleed holes to vent the vessel pressure to the atmosphere. Examples of venting to the atmosphere are U.S. Pat. Nos. 3,302,664 and 3,083,854 and German Pat. No. 1,072,127. However, as previously indicated, bleed holes by themselves tend to become blocked with dust, dirt or food residue or corrode shut when used on pressurized cleaning equipment in severe environments. Therefore, to prevent the problem of blocked bleed holes, the subject safety cap assembly has at least one bleed hole in addition to at least one venting channel. Consequently, should the bleed hole become filled with dirt or dust or corrode shut, the venting channel is available to alternatively vent the vessel pressure to the atmosphere as the closure cap is unscrewed.
In the past, it was common to use a cap assembly equipped with a lever arm operatively attached to the closure cap; consequently, the person opening the cap did not need to stand directly over the cap. However, if such cap was accidentally opened under pressure, it made little difference precisely where the person opening the cap was standing since the force of the suddenly release pressure would spray corrosive fluid in all directions.
The previous lever-arm type of fill port or cap assembly included a butterfly-type valve within the assembly. By its very design, it was able to open under high pressure and provided no safety factor. An air-operated safety interlock was often provided to prevent accidental opening of the fill port while the tank was pressurized. The corrosive cleaning fluids, however, often disabled the interlocks thus permitting accidental opening of the pressurized tank.
In short, the lever-arm type of fill port did not adequately protect against the possibility of the highly corrosive cleaning liquid being expelled onto the person opening it due to the sudden release of pressure.
This invention substantially solves the problems presented by the lever-arm type of assembly with three means. First, the subject safety cap assembly is equipped with a commercially available, externally threaded filler member which threadedly receives a commericially available closure cap. More specifically, the subject invention uses a Huber-Yale Figure 500, Series 150, four inch closure assembly although others are available. This closure cap and filler member are designed so that whenever the pressure within the vessel exceeds a predetermined pressure, the threads of the filler member and the threads of the closure cap interact in such a manner that it is not reasonably possible to unscrew the cap from the filler member.
Second, the subject safety cap assembly includes at least one bleed hole and at least one venting channel which are directed away from the face of the person unscrewing the safety cap. Therefore, if for some reason there is a sudden release of pressure as the cap is unscrewed, the corrosive cleaning liquid will be expelled in a direction away from the face of the person unscrewing the cap, thereby preventing any injury to such person.
Third, the subject assembly is equipped with a safety cage which extends about the closure cap and prevents the cap from becoming a dangerous projectile should the cap be blown off the filler member.